Reconstruction of paraffins



Juy 9, 1946. F. E. FREY RECONSTRUCTION OF' PARAIVFINS 2 Sheets-Sheet l Filed Feb. 6, 1942 F. E. FREY l yRECONS'IJRUCTION 0F PARAFFINS July `9, 1946.

2 Sheets-Sheet 2 Filed Feb. 6, 1942 Patented July 9, 19:46 o i RECONSTRUCTION F PARAFFINS; Frederick E. Frey, Bartlesville, Okla., assignor'v'to" Phillips Petroleum Company,

Delaware a corporation of Application-February ,6, 1942, Serial No. 429,810

1 This invention relates to the conversionof hydrocarbons. More particularly, it relates to chemical reconstruction of paraiins into, morev highly branched parains inthe presence of hydrouoric acid as av catalyst. This application is a continuation'in part ofy my copending application, Serial No. 426,627, led January 13, 1942.

An object .of this invention .is `to produce branched parafns fro-m relativelyY less highly branched paramns.

A specific object is to control, in `a, process forv converting parans in the presence of Vhydrofluoric acid, the proportions and :the molecular; Weight or volatility of thehydrocarbons producedY that differ in molecular weight fromV the'v feed.

material.

Another specific object is to produce W-boil# i ing isoparafns from normal butane.

Another specific object is to produce loW--boil-` ing soparans from normal pentane.

osition of non-volatile material in the reaction zone of a process for converting parainsin the presence of hydrofluoric acid.

Other objects and advantages of my invention will be apparent from the accompanying descrip-` tion and disclosure. Y

In the afore-mentioned copending application,

I have disclosed a broad process `for converting saturated hydrocarbons into saturated lhydrocarbons of different skeletal congurationsand, in part, ,of different molecular Weight by the ac-A tion of hydrofluoric acid. This process involves several dierent types of chemical reactions. The predominating reaction types, as deduced from a consideration of reactants, products, operating conditions, and theoretical'oaspeots relating to the invention, may be exemplified as follows: Y

The rst two reactions, namely, reconstruction to produce both higherand lower-boiling par- Y I Another specific object is to minimize the dep- 13 claims. (c1. 26o-6835 v 2 Y ailins, and isomerization, respectively, predominate .under relatively mild treating conditions. The yield of cyclics, exemplied in the third equa- `tion bycyclohexane, is increased by increasing the Jtemperature and/or the time of reaction.

ArfourthV type of reaction is believed tor account` for the increase in saturation and stability that occurswhen motor fuel comprising some unsat,

f urated material is treated. By this reaction, olefins are converted lto cycloparaflins such as cycloheXane and its derivatives. This reaction may beeXemplied as follows: o

HF f

Several other types of reactions undoubtedlyoccur in the 'reconstruction process; however, the above-mentioned ve types appear to account forv `mostof the eects which arer produced. The

general term reconstruction is used herein toV denote the production of one or more of the above-mentioned effects and/or of other inherent advantageous effects which result from the 'Y practice of my invention.

The present invention is concerned With the' gas-phase conversion of predominantly parafiinic hydrocarbons of comparatively low molecular weight into more highly branched isomerie parafnic hydrocarbons and, in part, into saturated hydrocarbons of. lower and higher molecular Weight. I have found that, inthe presence of substantial vproportions of hydrogen fluoride and under' suitable conditions of temperature and time, parafn hydrocarbons of relatievly 10W molecular Weight, such as normal butane and/or normal pentane, can be converted in high yield to isomeric branched paraflins, such as isobutane and isopentane. Further, I-have found that paraiiins of higherr andlower molecular Weight can also be produced under similar conditions, concurrentlyV With the production ofisomers, and that the proportions and the molecular Weights ofs'uch products can be controlled by suitable recycling steps; for example, isobutane can be produced'as the major product fromone or more parafns having four to ve carbon atoms per molecule, of which at least four carbon atoms are in a/ straight chain. `Still further, I have found thatv relatievly Vnon-volatile material,

which is formed in small proportions and Whichv would' otherwise be deposited and carbonized upon Vthe surfaces of the reaction zone, can be.

removed .by scrubbing the reaction zone,v intermittently or continuously, with a liquid hydrocarbon which is relatively non-volatile at the reaction temperature.

In general, my investigations have shown that, when a relatively low-.boiling paraffin hydrocarbon material having at least four carbon atoms per molecule, in a straight chain, is subjected to the action of substantial proportions of concentrated hydroluoric acid under suitable reaction conditions, there results a mixture comprising propane, isobutane, normal butane, isopentane, normal pentane, hexanes, and higher-boil.- ing hydrocarbons. Any of these hydrocarbons, especially if present in relatively large proportions in the original mixture or feed material,

tends to be converted to hydrocarbons which are.

originally absent or present only in small proportions. Thus, by separating out the desired products and recycling the others, very high u1- timate yields of the desired products can` be obtained. In one specific embodiment, the present invention is directed particularly to. the production of iobutane and/or motor-fuel hydrocarbons from normal paraflins having four to live carbon atoms per molecule.

As the catalyst,Y hydrogen fluoride may be used in the following ways: alone; with relatively small proportions of modifiers such as water, basic organic nitrogen compounds, and/ or salts; and/or inv conjunction with solid contact` masses or sur'- faces, preferably those which comprise iron and/or alumina, such as steel shavings, aluminaA gel, bauxite, and the like.

Conversion stocks for the process should be composed of saturated hydrocarbons containing preferably little or no unsaturated hydrocarbons; they may comprise normal butane, normal pentane, and/or higher paraffns, provided that they are not so high-boiling as to make gas-phase conversion not feasible. tions of undesirably low ostane number or of volatility other than that desired for some particular purpose may be used; such fractions may comprise either distillates as they ordinarily ccur in the industry or fractions of inferior octane number obtained upon removing constituents of superior octane number from existing stocks. The conversion stock may also comprise residues from the application of selective solvent treating, azeotropic distillation, or the like to separate hydrocarbons having relatively enhanced value when separated from each other.

An understanding of some aspects ofmy invention may be aided by the accompanying drawings, wherein Figure 1 and Figure 2 are flow-diagrams showing diagrammatically two specic arrangements for practicing my invention. Corresponding parts in each figure are designated by the same numerals.

In the embodiment of Figure 1, a hydrocarbon material, which for the sake of simplicity may be taken to be chiefly or substantially entirely normal butane, is admitted through inlet II, valve I2 and charge pump I3 to conduit I4, whereinl it is mixed with concentrated hydrouoric acid, which is admitted through inlet I5, valve I6, and charge pump I 1. The proportion of acid may be Vfrom about 0.1 to 4 times or more by weight of the hydrocarbon material; preferably, it is in the range of.0;2 to 2 times by weight of the hydrocarbon material. The use of very small proportions results in slow or incomplete conversion, andthe use of very large proportions causes a decrease in the production capacity of the equipment.

The resulting hydrocarbon-hydrofluoric acid mixture in conduit I4 is passed to heating coil I8, in which it is heatedto the desired reaction temperature. The temperature should be so high that the reaction mixture is in the gaseous condition; it usually may be within the range of about 250 F. or less to 1000 F. or more. Usually the optimum temperature is in the range of 400 to 800 F.; at lower temperatures, the conversion is relatively slow, and at higher temperatures excessive cracking and/or dehydrogenation occurs. The pressure may be within the range of about atmospheric to 5000 pounds per square inch or more; usually the optimum pressure is in the range of 250 to 2500 pounds per square inch. At low pressures, since the volume of reactants is relatively large, a reaction -chamber of comparatively large size is required; at high pressures, relatively expensive high-pressure equipment is required. In any particular instance, the most economical operating pressure may be determined by -a study of the various factors involved in the various possible alternatives.

From heating coil I8, the mixture is passed through Valve I9 and conduit 20 to reactor 2|, wherein it. is maintained at the reaction temper- `ature for a time sufficient to effect the desired system.

Petroleum distillate frac- There is a tendency for small proportions of relatively nonvolatile hydrocarbons, which are formed incidentally in the reaction zone, to accumulate and to carbonize or form coke on the walls of reactor 2|. This action may be advantageously minimized by scrubbing the reaction zone with a high-boiling oil, such as mineral seal oil, to absorb and remove the nonvolatile material substantially as soon as it is formed. The scrubbing oil is admitted through inlet 22 having valve 23 to distributing means 24 near the top of reactor 2|. The proportion of scrubbing oil is preferably from about'0.1 to about 1.0 times by weight of the hydrocarbon reactants.4 Smaller proportions are sometimes insufficient t0 effect the desired absorption, and larger proportions sometimes tend to interfere by the oil undergoing reaction itself. The reactor is so designed that the time of residence of the scrubbing oil therein is relatively short, preferably of the order of a tenth to a hundredth of the reaction time, in order to minimize reconstruction or cracking of the oil itself.

Reactor 2I usually need not contain any packing, or the like, so that the scrubbing oil simply falls from top to bottom as a spray; in some cases, however, especially those in which the reaction time is relatively'long, it preferably is loosely packed With a suitable contact material resistant to corrosion by concentrated hydrofluoric acid. Among contact materials may be mentioned metals, such as various steels, Monel metal, alloys of chromium, nickel, magnesium, and/or aluminum and the like, and granular substances, such as alumina, bauxite, carbon, and the like.

The eflluent from reactor 2| comprises the reamante.

action mixture, chiey of hydrogenfluoride andv bon phase, as by gravitational or centrifugal means. n Y

The scrubbing-oil phase may be recycled through valve 28, conduit 29, and pump 30 to the top of reactor 2|. Preferably, however, at least part of it is passed through valve 3| and conduit 32 to fractionator 33-,Ywherein'it is purified, for example by separation intovthe following three fractions: '(1) a `minor lfraction comprising hydrocarbons boiling below the temperature in reactor 2|, which may be withdrawn through outlet 34 having valve 35 lbut which isusually preferably passed through valve 1I to conduit 40; (2) a large fraction of relatively unchanged absorbing oil, which is recycled through valve 36 and pump 30 to the top of reactor 2|; and (3) a minor fraction comprising very high-boiling or semi-solid material, which is withdrawn through outlet 31 having valve 38'. V

The gaseous phase from separator 21 is passed through valve 39 and conduit 40, preferably together with the lowest-boiling fraction from fractionator 33, to partial condenser 4I, wherein relatively high-boilin`g materials, lfor example thoseboiling higher than the hexanes, are condensed: Suitable conditions may b'e suchas,-for example, a temperature of 450 F. anda pressure `of 450 poundsper-square inch. If it is `desired to use a lower pressure, a correspondingly lower temperature is used; for example, at r100 pounds per square inch the condenser temperature may be about 300 F; The resulting mixed VVphases are passedv through valve 42 and conduit y43 to In separator 51,the gas pliase'fromseparatorj is separated -intotwo liquid phases', as by cooling f and gravitational l-means f. The heavier orl hydroiiuoric acid phase is recycled'through valve 58 and c0nduit`54'to heating coil I8.r The lighter or hydrocarbon phase is passed through valve 59 A and. conduit 66 to vfractionating means 6I,

togetherk with the hydrocarbon phase from separator 12.

In fractionating means 6I, these hydrocarbon materials are fractionally distilled to yield ank isobutane fraction and any other desired Propane and hydrofluoric acid pass, at`--least partly as" an azeotropic mixture, Vthrough valve 64, and are recycled to coil|8 by conduit `65;'if desired, excess propanemay be 'withdrawnggas through outlet 62 and vvalve |53;v Isobutane is withdrawn through outlet 66 having valve '61.

Normal butane is recycled through valve 68 andconduit 65. Hydrocarbons heaviervthan butane Y may bel recycled with the normal butane, espe` vcially if `the highest possible yield ofisobutane 1 is desired; but if desired, selected lor especially valuable fractions may be advantageously` with-.- drawn; `for example, isopentane may be with-- f drawn through valved outlet 69, and/or material separator 44, wherein they are separated by gravity. v The resulting liquid phase, which comprises cyclics, acid-solubles, and other material, for example hydrocarbons boiling in .the hexane range and higher, is withdrawnthrough outlet 4|5 having valve Mi., The gas phase which comprises chiefly hydrofiuoric acid, and hydrocarbons of up to about .six carbon' atoms per 46 to second partial condenser 49.

In partial condenser 49, pentanes, hexanes, and most of vthe hydroiluoric'acidL are condensed.

molecule, is passed `through conduit 41 and valve' Suitable conditions may be such as, for example;`

a temperature of 325 F.v and a pressure of'400 pounds per square inch, or Ia temperaturev of' 225 F. and a pressure of 100- poundsper square inch. The exact optimum lconditions for any particular case may be readily determined by trial. The resulting mixed phases are passed through .valve 59 and conduit 5I to separator `452,

wherein they are separated by gravity. The

f of temperature and pressure forl atime suilicientresulting mixtui'eof liquid phases 'passeslthrough 52 and 12 are preferably so elevated in position that the recycling of the acid phase is advantageously effected by gravity, without the use of apump.

' The gaseousfphase from separator `f5 2is Apassed, through valve'55 and conduit 56 to 'separator '51.'

-boiling above normal butane or above isopentane ymay be withdrawn through valved outlet 10. j

yIt is understood that iractionating means 6I.` may. comprise whatever distilling columnsf'and;r auxiliary equipment 'appear necessary or conven-f Aient for effecting the separations indicated. ylf desired, any of the fractions withdrawn may be subjected to one or more 'purification steps .notshown, such as, for exampla deiluorination by.

contacting with bauxite at a suitable temperature.

In the embodiment.l of-Figure 2, a hydrocarbon material, which for the sake of simplicity may be taken to bef chiefly or substantially entirely normal pentane, is `admitted through inlet II,

valve I2, and lcharge pump I3, toV conduit I4, y

wherein it is mixed with concentrated hydrofluoric acid,. which is admittedthrough inlet I5, valve I6, and 'charge pump I1.` Theresulting hydrocarbon-hydrouoric acid mixture is passed toheating coil I8, in which it is'heated. to'th'e i desired reaction temperature-. The `preferred` proportions, of -hydroiluoricf facidand the prel ferred reaction conditions'for this embodiment of my-invention aresubstantially the same asforthe embodimentshown in Figure 1', and,

previously discussed. The heated reaction mixture from coil I8 is passed to reactor2l, wherein it is subjectedvto the desired reactionv conditions to effect the desired. extent of reaction. If

.desired, reactor 2| may be packed with steel turnings or.. otherv solid material suitable for aiding'in the lcatalysis of the reaction Y. v

f The )eliiuent mixture from lreactorZ I through conduit 2'5, having valve/26 to -sepaatrator 21, wherein itis separated into two liquid phases,v

as by @001mg and means. y

The heavier or hydrouoric acidi phase'imay be 'y 'gravitational' or centrifugal recycled through valve 15 andjconduit 16 to'pump- I1.' Preferably,'hov'vever, at least Apart '0f-it 'is passed through v'alvc11 and conduit 18 tohfracl tionator 19, wherein it is separated int'othefollowing two 'fractions :1 (1^) an overhead fraction drous hydrofluoric'v comprising substantially a4 acid with small proportionsfof'light'hydrocarbsf such as.- .propane-:and ebutane, which is. recycled through valve 80and conduit `1.6 .to pump VI1,'and

(2) a"v minor bottom .fraction comprising acidsoluble material, water, `and hydrogenfluoride, which is Withdrawn 'through outlet..8I-having.

valve 82. f f

The lighter or hydrocarbon phase from separator 21 is passed through valve 83 and conduit 84 to fractionating means 85, wherein it. is fractionally distilled to yield an isobutane fraction and any other desired products. Light gases, such'as methane, ethane, and thev like, are! preferably withdrawnfrom the system, as through outlet 86 having valve 81. Propane and hydrofluoric acid. pass, at least partly as an' azeotropic mixture,

may be advantageously withdrawn. For exacrnple,- isopentane may be Withdrawn-through outlet 93 having Valve 94; normal pentane is preferably recycled through valve 95 and conduit 89;v and material boiling above normal pentane maybe withdrawn through. outlet 96 havingy valve 91.

Fractionating means 85 may comprise Whatever distilling .columns and auxiliary equipment are necessary or convenient for effecting the separations indicated.

If desired, any ofthe fractions Withdrawn from' fractionating means 85 may be passed through mover |00, which contains a contact lmass hav-- ing hydrogenation and/ or dehydrogenation propertles, such as bauxite, alumina, or other similar catalyst.y Usually suitable operating conditions are a temperature in the range of '75 to 400 F. and a space velocity inthe range of 1 to 50 volumes of liquid hydrocarbon material per volume of catalyst per hour. Under such conditions, which maybe particularly selected in accordance with the results of a trial for the particular case organically combined fluorine is substantially completelyfremoved from the hydrocarbon material, which then .is passed through valve IOI and conduit" |02 to fractionator |03 for separation into any desired final fractions.' A substantial fraction comprising motor-fuel hydrocarbons may be withdrawn through outlet |04 having valve |05, andav minor'fraction comprising hydrocarbons boiling above the motor-fuel range may be withdrawn vthrough outlet |06. having valve |01.

-The volatility of the motor-fuel product is Iadvantageously controlled by adjusting the proportion of relatively light constituents, any excess of which is recycled from fractionating means 85.

For example, if a relatively volatile motor fuel is desired, less of these light constituents is.reI

tom of fractionator |03. -If desired, part or all of the above-mentioned high-boiling constituents maybe recycled, by iheansv not shown, to pump I3;` usually, however,V it is preferable -to removethis'material from the system, because it 4tends to carbonize- `inV the heater. and/or reactor.

VAlthough the isobutane product from fractionating means may be subjected to oneor more purification steps,. such as defluorination or the like, it usually need not be purified, especially if it'isto be used as feed to an` alkylationprocess catalyzed by a hydrorluoric acid catalyst.

Some aspects of my'invention are illustratedA in the following examples, which are illustrative, but not necessarily limitative, of the invention.

lEzrampze I A hydrocarbon stream consisting of substanitially pure normal'butanel is subjected to the action of 50 per cent of its weight of concentrated hydroiluoricv acid in aprocess similar to that described in connection with Figure l. The reaction temperature isab'Out 650 F., the pressure is .about '150 pounds per square inch, and thereaction-"time is about 30 minutes. packed'fwith steel turnings; and about 5 per cent, byweight of hydrocarbon treated, of a high-boiling absorber' oil -is passedv continuously throughthe vreaction Zone' to prevent coking'up' of the re-` actor. yUnder theseconditi'ons the ultimate yieldv of isobutaneis about 75 per cent by weight of the normal butane feed. Of'the other 25 per cent, about 10 per centis convertedto` propane; and aboutV 15 per cent.: to heavier hydrocarbons.

A hydrocarbon stream 'consisting mainly of normal pentane is rsubjected to the action 'of about 70 per cent of its 'weight of' substantially 'anhydrous hydrofluoric acid ina process similar to-that described in connection With Figure'Z. *The reaction temperature is about 700 F., the pressure is about 1000 pounds per square inch, and the reaction time is about 20 minutes. Pentanes in the product arer recycled. Under these conditions, the yield `of motor-fuel hydrocarbons having 6 or more carbon atoms per molecule is about 25 per cent by weight of the material charged, and the yield of isobutane is vabout 60 per cent; the remainderis 4'convertedto propane and to material boiling above the motor-fuelrange.

Example III` In a batch procesa-normal butane Was treated In a corresponding continuous process, in which reaction conditions are comparable but in whichrecycling gis.practiced, the major-product Withdrawn .fi.s.-fis,ebutanei.isppentane and/0r higher Reactor 2 is Iboiling hydrocarbons maybe also" withdrawmhut if desired,`.they maybe recycled to increase the ultimate yield of isobutane.

` i K Example IV In abatch process, normal pentane was treated in a steel reactor with twice its weight of concentrated hydroiluoric acid. The maximumtemperature, reached in about one hour after starting the heating, was 572 F. This'temperature was maintained for -30 minutes; then the reactor was cooled rapidly, and the products were withdrawn for examination. On a normal pentanefree basis, theproportions of the various prodn apparent vfrom lthese* data that, in a icor-- responding continuous process, by recycling undesired productsespecially propane and/or norma,1-.hutane,1.ri0rma1 pentaneecan V.be converted high` yield to isobutane Yand/Q1 ,isopentane and/or motorfue1hydrocarbons g l In 4asteel bomb, nomalbutane wassubjected to the-action` of twice its Weight of concentrated,

,hydrofluoricacid at a maximum temperature of --3. 5 6 F. and a pressure of 3700 poundsV per square finch for a, period of three hours. ',Ihe bomb'was cooled, and the vproducts were withdrawn. The .hydrocarbon material recovered had the follow- .,iscomvqsia. 'A

" fAlthog'hg'fi'n this' exampm, theractipn conditions'were obviously 'very unfavorable', an appreci--fy "able reaction did-occun" the conditions used "are Ytherefore, vconsideredy tojbe'within the broadest scope of-this invention.

Ezrample VI Isopentane and about 60 per cent of its weight of concentrated hydrofluoric acid were'allowed to stand Vin a steel bomb for fourweeks at ajtemperature ofV 175 F.j Then the products vwere withdrawn, and the resulting hydrocarbon mal terial was found to have approximately the following,composition:

'Poductzff 'j Y ,l ,Mol percent Butanes (mostly isobutane) f 8.6 Elsopentane V K 69.6

Hexanes and heavier 11.5

'Althoug'h, inthis example the spntanewas `mostly.inthe liquid phase because of the rela- ?,tively low temperaturafthe results show thatiso- .Qlentaneban betreated land/or recycledjto give fappreciable .yields of. isobutane; also, .they indi.

cate vthat, isopentane canl be `converted .to any desired extent into relatively heavygmotQr-ffuel hydrocarbons, whereby control ofthe' volatility of relatively heavy, products may be advantageously obtained inthe manner' generally scribedherein. 1 f 4 My invention provides a new 'process for con-l vertingnormal butane and/or, pentane to isobutane. It is applicable valso to the'production of isopentane, forexample by the conversion of normal pentane and/or heavier paraidns toisopentane. yIt would also .be possible to lconvert isobutane and/or isopentanetoanormal butane and/or normal pentane, respectively, by thisv invention, if a need for such a conversion should arise.A Motor fuel of controlled Volatilityjcan be vproduced in substantial propOlftions'as a product ofmy process. VMy invention comprises also a novel means for preventing coking up of reaction chambers used in the process. Furthermore, it provides aA simple method of separating` heavy acidfsoluble material from hydroiiuoric acid which is to be recycled.

There are many modifications of my process,

of which only a few are described in this specification. Hence, it is not intended thatmention herein `ci? specific apparatus, materials, conditions, purposes, or the Ylike should unduly limit the scope of my invention. In the specific em- .bodimentsdescribedit is understood that addivtionalequipment such as pumps, valves, coolers,

fractionators, or the like, such as are well-known to those skilled in l.the art, may be` used wherever needed or convenient. Y Y Y,

Iclaim;

LA process for isomerizing 10W-boiling paramnjhydrocarbonsjof at least four carbonvatoms per moleculein a straight chain to form lowboiling isoparaflins, whichcomprises subjecting in a reaction zone sucha paran to the action of hydrofluoric acid as the sole effective isomerization catalyst, in an amount from about 0.1 `to 4 times by weight of the hydrocarbon material,

under an elevated vtemperature and pressure such that said paraffin and hydroiluoric acid arey in gas phase, passing a minorl amount of a heavy voil through said reaction zone .as a liquid to ab sorb reaction products of high molecular Weight andv minimize carbon and tar formationpass ing eilluents of said reaction zone to a first-separator andremoving as a liquid said heavy oil tion zonecontains a solid contact mass.

and absorbed constituents, removing falso from said I'lrst separator as a Vgasa mixture of low-boiling hydrocarbons and hydrofluoric acid, subjecting said gas to partial cooling and condensation to liquify hexane and heavier hydrocarbons and removing the resultant liquid from the process, subjecting ythe remaining gas to further partial cooling and condensation to liquify themajor 60Y 'frorn.v uncondensed gas, cooling and condensing fs'aid uncondensed gas to form a liquid hydroportion of hydrofluoric acid, and separating same uoric acid phase land a liquid hydrocarbon phase, passing said liquid hydrocarbon phase to a fractional distillation andY recovering therefrom low-boiling isoparaiiins.

2 .LThe process of claiml, in which said elevated temperatureis in the range of 250to 1000?` F.

3. The process of claim l, inwhichsaid elevated temperature is in the ranges of L1to0-800" F.

4. The process of claim 1, wherein the reac- 5.Theprocess' of; claim, Lin, which Said' par- `Vaiin is no rmal pentane Vand'in which saidisop'flir amnsouproducedis;isobutane.

6. A process for converting low-boiling paraffin hydrocarbons of at least four carbon atoms per molecule in a straight chain to form low-boiling isoparafiins, which comprises passing such a paraiin in admixture with hydrofluoric acid as the sole effective conversion catalyst, amount from about 0.1 to 4 times by Weight of the hydrocarbon material, through a large lvertical reaction zone, maintaining the mixture in said reaction zone in gas phase under an elevated temperature and pressure for a time to effect a substantial conversion of said paraffin to form low-boiling isoparafiins' including at least one isomer of said paraiiin, introducing at the top of said vertical reaction zone a heavy hydrocarbon oil which remains in liquid phase under said conversion conditions to absorb reaction products of high molecular weight and minimize carbon and tar formation, passing eilluents of said reaction zone to a first separator and removing as a liquid said heavy oil and absorbed constituents, passing said liquid to a fractionating meansand removing low-boiling hydrocarbons absorbed therein, removing a gas from said rst separator and admixing said low-boiling hydrocarbons with said gas, subjecting the resultant mixture to partial cooling and condensation to liquify hexane and heavier hydrocarbons and removing the resultant liquid from the process, subjecting the remaining gas to further partial cooling and condensation to liquify the major portion of hydroluoric acid together with some pentanes and hexanes, and separating same from uncondensed gas, separating the resulting liquid into av hydroiiuoric acid phase and a hydrocarbon phase and returning said hydrofluoric acid phase to said reaction zone, cooling and condensing the last said uncondensed gas to form a hydrofluoric acid phase and a hydrocarbon phase and returning said hydrofluoric acid phase to said reaction zone, combining the two last said liquid hydrocarbon phases and passing same to fractionating means, and recovering from said fractionating means low-boiling isoparafiins so produced.v

.7. The process of claim 6,'wherein the propor-l tion of absorbing fluid is inthe range r0.1 tol times by weight of the Vhydrocarbon material vtreated and its residence in the reaction zone is not greater than one-tenth that of the Vparaffin undergoing conversion. n

8. A process for converting a low-boiling paraiiin having at least four carbon atoms per molecule to form other low-boiling parafns, which comprises passing a gaseous mixture comprising such a low-boiling paraffin and hydrogen iiuoride as the sole conversion catalyst downwardly through a reaction Zone while at a conversion temperature in the range of about 250 to 800 F., maintaining said mixture in said reaction zone for a time sufficient to convert a substantial amount of said parailin forming other low-boiling parainns including at least one isomer of said parain, concomitantly passing downwardly through said reaction zone in liquid phase a: heavy oil to absorb-reaction products of high molecular weight and minimize tar and carbon formation, said oil being passed through said'zone at a rate such that it undergoes substantially no conversion, and separating from effluents of said reaction zone low-boiling hydrocarbons produced therein.

9. A process for isomerizing a low-boiling paraffin having at least four carbon atoms per molecule to form other low-boiling paraffins, which comprises passing a gaseous mixture comin an` y such as to scrub the inner surfaces of said reac- I2 prising such a low-boiling paraflinand hydrogen iiuoride as thesole isomerization catalystthrough a reaction zone while at an isomerization temperature in the range of .about 250 to 800 F., maintaining said mixture in said reaction zone for a time suiiicient to isomerize a substantial amount of said parairin forming an isomer thereof, cooling and effecting a partial condensation of eilluents of said reaction zone to condense and remove as a liquid heavy cils, Subj ecting remaining vapors n to Vfurther cooling and effecting a p'artialcondensation thereof to condense a major part of the hydrogen fluoride and of remaining Ahydrocarbons heavier than `butane, separating from the last said partially condensed 'mixture liquids so formed and uncondensed vapors, separating from said liquids liquid hydrogen fluoride and liquid hydrocarbonY as separate materials, subjecting said uncondensed vapors to Vadditional cooling and condensingto form a second liquid hydrogen uoride phase and a second hydrocarbon-phase, combining Y said liquid hydrogen fluoridephases and passing same to said reaction zone, combining the last two said hydrocarbon phases and subjecting same to fractional distillation, recovering from said fractional distillation normally gaseous-paralin hydrocarbons and a -minor amount of hydrogen fluoride and passing same to said reaction zone, and recovering also Vfrom said fractional distillation low-boiling isoparaflins as products of the process Y 10. A process forv converting a low-boiling paraflin hydrocarbon havingat least four carbon atoms per molecule to otherlow-boiling paraffins, which comprises passingtothe top of an elongated verticalreaction zone in vapor phase a paraffinic hydrocarbon material comprising such a low-boiling paraffin and hydrogen iiuoride as the sole eiective catalystin an amount between about 0.2 and about 4 times byvweight of the hydrocarbon material, maintaining the resulting gaseous mixture of hydrogen uoride and paraflinic hydrocarbon material in said reaction zone ata conversion temperature between about 250 and about 800 F. and undena superatmospheric pressure for a reaction/time suicient to form other low-boiling paraflin hydrocarbons including at least one isomer of said low-boiling parafiin, injecting into the top of said reaction zone a liquid hydrocarbon material in a manner tion zone and maintain the same free of carbonaceous deposits, said liquid hydrocarbon material being relatively nonvolatile at said reaction temperature and passed through said reaction zone at a rate such that its residence time therein is'not greater than 0,1 times said reaction time, and recovering from the bottom of said reaction zone hydrogen fluoride, reaction products, and said liquid hydrocarbon material.

11. The vprocess of claim 1.0 in which saidmaterials eiliuent from said reaction zone arepassed as a single eiiluent mixture to a separator, separating therefrom a liquid phase comprising said lliquid hydrocarbon material and a gas phase com# prising hydrogen iluoride and parainic reaction products, returning aportion of said liquid phase tothe top of said reaction zone, subjecting a further portion of said liquid phase to purification to remove volatile material and liquid impurities, recovering a puriedliquid hydrocarbon material and passingsame to the top Iof said reaction zone, combining said volatile [material .with said gas phase and .recovering therefrom a hydrocarbon 'fraction comprising an isoparamn 13A produced in said reaction zone as a product of the process.

12. The process of claim 10 in which the reaction zone is packed with granular alumina.

13. A process for converting a low-boiling parafn having at least four carbon atoms per molecule to form other low-boiling parains, which comprises passing a gaseous mixture comprising such a low-boiling paraffin and hydrogen fluoride as the sole effective conversion catalyst, in an amount from about 0.1 to 4 times by weight of the hydrocarbon material, downwardly through a reaction zone While at a conversion temperature in the range of about 250 to 800 F., maintaining said mixturensaid reaction zone for a. time sufcient to convert a substantial amount o! said paraffin forming other low-boiling paraiins, including at least one isomer of said parain, concomitantly passing downwardly through said reaction zone in liquid phase a heavy oil to absorb reaction products of high molecular weight and minimize tar and carbon formation, said oil being passed through saidzone at a rate such that it undergoes substantially no conversion, and separating from eluents of said reaction zone 

